[gmx-users] dipole moment of a charged peptide

Dommert Florian dommert at icp.uni-stuttgart.de
Fri Apr 1 09:45:33 CEST 2011

On Thu, 2011-03-31 at 18:03 -0700, Sanku M wrote: 
> Hi,
>    I have a long-chain peptide which has a net charge of  +5 . I was
> wondering whether the g_dipole will give any reasonable dipole moment
> for a molecule with a net charge. Is there any suggestion I should
> follow regarding calculation of dipole-moment of a charged molecule .
>  I found that in the manual it is mentioned that 'For molecules with a
> net charge, the net charge is subtracted atcenter of mass of the
> molecule.'.  I did not understand what it means. I am using
> gromacs-4.0.7.
> Sanku

If you have a charged molecule the dipole moment is not unique, so you
have to choose a reference point and this can be done by subtracting the
net charge at this point. Write down the formula and rearange the terms
and you will clearly see, what I mean.


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Florian Dommert
Dipl. - Phys.

Institute for Computational Physics
University Stuttgart

Pfaffenwaldring 27
70569 Stuttgart

EMail: dommert at icp.uni-stuttgart.de
Homepage: http://www.icp.uni-stuttgart.de/~icp/Florian_Dommert

Tel.: +49 - (0)711 - 68563613
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